OPN3

G protein-coupled photoreceptor that selectively activates G(i/o) proteins in response to light, thereby decreasing intracellular cAMP levels. Activation occurs when the opsin-bound cis-retinal chromophore absorbs a photon and isomerizes to all-trans-retinal, inducing a conformational change in the opsin that triggers a G protein-mediated phototransduction cascade. Mediates blue light-induced pigmentation in melanocytes by activating calcium/CAMK2 signaling, followed by phosphorylation of CREB, p38, ERK and MITF. Required for TYR and DCT blue light-induced complex formation in melanocytes. Involved in keratinocyte differentiation in response to blue-light. Plays a role in melanocyte survival through regulation of intracellular calcium levels and subsequent BCL2/RAF1 signaling. Additionally, regulates apoptosis via cytochrome c release and subsequent activation of the caspase cascade. Responsible for ultraviolet A (UVA)-induced keratinocytes supranuclear melanin cap formation via activating calcium/CAMK2, CREB, and Akt signal transduction, and ultimately increasing DYNC1I1 and DCTN1 expression levels, thereby playing a role in the skin response to UV radiation. Required for the UVA-mediated induction of calcium and MAPK signaling resulting in the expression of MMP1, MMP2, MMP3, MMP9 and TIMP1 in dermal fibroblasts. Also plays a role in light-mediated glucose uptake, mitochondrial respiration and fatty acid metabolism in brown adipocyte tissues. May be involved in photorelaxation of airway smooth muscle cells, via blue light-dependent GPCR signaling pathways (By similarity). Also inhibits melanogenesis in melanocytes by specifically inhibiting MC1R-evoked cAMP signaling in a constitutive, light-independent manner. In the paraventricular nucleus of the hypothalamus, inhibits MC4R-mediated cAMP signaling and activates KCNJ13 channel opening in a constitutive manner, thereby promoting food intake and modulating spontaneous firing of neurons..

Function from UniProtKB (Q9H1Y3), read 2026-09-23. CC BY 4.0.